Compressional wave radiator



July 16, 1946. w. P. MASON 2,403,990

v COMPRESSIONAL WAVE RADIATOR Filed Aug. 1, 1942 4 Sheets-Sheet l RECTIFIER INVENTOR W F. MA SON A ARNEV July 16, 1946. w. P. MASON COMPRESSIONAL WAVE RADIATOR Filed Aug. 1, 1942 4 Sheets-Sheet 2 :llinnni-i IJH L //l. Ti

FIG. 5

lNVENTUR W R MASON ATTORNEY July 16, 1946. A w, MASON 2,403,990

CO'MPRESSIONAL WAVE RADIATOR 4 Sheets-Sheet 3 Filed Aug. 1, 1942 Ii Ii INVENTOR W R MASON ATTORNEY July 16, 1946. w MASON 7 2,403,990

COMPRESSIONAL WAVE RADIATOR I Filed Aug. 1, 1942 4 Sheets-Sheet 4 INVENTOR w F. MASON ATTORNEY Patented July 16, 1946 dOliIPRESSIONAL WAVE RADIATOR Warren P. Mason, West Orange, N. J.,' assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application August 1, 1942, Serial No. 153,225

14 Claims. 1

This invention relates to submarine signaling and more particularly to a compressional wave radiator.

An object of the invention is to radiate com-. pressional waves under water.

Another object is to convert a shock wave into a vibration of limited frequency range.

A further object is to increase the duration of the vibration radiated.

Another object of the invention is to increase the output of a compressional wave radiator falling within a limited band of frequencies.

Shock waves having large energies for a short period of time have been employed heretofore in submarine signaling systems. Such a shock wave has its energi spread quite uniformly over a very wide frequency range but, in a typical case, dies out in about two milliseconds, In some submarine signaling systems, however, there is required a compressional wave which will persist at a high energy level for a much longer time.

In accordance with the present invention there is provided a submarine compressional wave radiator which will deliver the required type of wave. The radiator comprises a water-tight container filled with liquid, means within the container for delivering a strong impulse to the liquid and filtering means associated with the container for transmitting therethrough a limited band of frequencies. The impulse may, for example, be generated by an electrical discharge through the liquid in the container. The filtering means preferably comprise a pair of metal diaphragms, rigidly supported at their peripheries, and an interposed layer of elastic material having a comparatively low Youngs modulus. A satisfactory elastic material is resin, such, for example, as cellulose acetate or polymerized methyl methacrylate. The mid-band of the filter is placed at the frequency at which it is desired that the peak of energy shall occur. The band width is made sumciently narrow to ensure the desired duration of the pulse, since the narrower the band the longer it will take for the output to die down to a given fraction Of its initial value. In order to increase the power output of the radiator, more than one filter unit may be provided. The container may take the form of a parabola, a cylinder, a sphere or any other suitable shape.

The nature of the invention will be more fully understood from the following detailed description and by reference to the accompanying drawings, in which like reference characters refer to similar or corresponding parts and in which:

Fig. 1 shows, partly in section and partly diagrammatically, a parabolic-type of compressional Wave radiator in accordance with the invention;

Fig. 2 is asectional view taken along the line "2 of Fig. r v Fig. 3 is a schematic circuit of the mechanical filter unit used in the radiator;

Fig. 4 is a sectional view of a cylindrical type;

of radiator;

Fig. 5 is a sectional .view takenamhgth l n 5-5 of Fig. 4;

.Fig. 6 is a view, partlyfin section, of a spherical type of radiator; and I Fig. 7 is a perspective view, partly exploded, of parts of the radiator-. of Fig. 6.

Taking up the figures in more detail, Figs. 1 and 2 show a compressional wave radiator comprising a water-tight container l0 formed of a parabolic metallic reflector ll closed by two circular metallic end plates l2 and IS. The refl' e q tor l l has an'annular flange [4 to which the inner plate I2 is secured by means of screws'such as 15.

A number of circular holes. suchas l8 are drilled in the outer side of the .plate l2, leaving comparatively thin diaphragms H! which are rigidly supported at their p ripheries. A corresponding number of matchin circular holes such as 2 0 are drilled in the inne side of the plate [3, leaving thin diaphragms 2 Between each pair of diaphragms l9 and 2i "andcemented thereto is a cylindrical plug 23 made of an elastic material for which Youngs modulus is. comparatively low. Natural or synthetic resin such, for example, as

cellulose acetate or polymerized methyl methacrylate is a suitable material. The plate I3 is fastened to the plate l2 by means of screwssuch as 24. The container Ill may, for example; 'be

mounted on the side or bottom of a ship in such a way that the reflector I l extends inside the ship through a hole 251 in the'ships plate 26, and it;

may be secured by'meansof bolts such as .21

which go through the ships plate 26, the flange l4 and the plate l2. A gasket 28 prevents water from leaking through the joint.

"The container Ill is filled' with fresh or dis-v or other liquid having a comparatively high resistivity. The source of the impulse is an electricaldischarge across the gap 30 between'the ends of the electrodes 3| and 32 within the container H). The electrode 3| is electrically tilled water connected -to the reflectorl I but the electrode 32' is insulated therefrom by means of the insulator focus of the parabolic reflector ll; 7

The required voltage is derived from the alternator 35, rectified by the rectifier35 and used A The center of the gap 3|] is pl-aced at the to charge the capacitor 37, one side of which is connected to the reflector II at the point 38 by the lead 39 and the other side of which is connected through the switch 49 and the lead M to the insulated electrode 32. When the switch 40 is closed there is impressed across the gap 30 a voltage sufiiciently high to cause between the electrodes 3I.,and 3.2 an electrical. discharge which delivers a strong impulse to the liquid within the container II. This impulse is transmitted through the liquid to th inner plate I2.

A diaphragm I9 in the plate I2, a corresponding diaphragm 2| in the plate l 3 and the interposed plug 23 constitute a mechanical wave filter IS the equivalent T network. or. which. is shown schematically in Fig. 3. Each; seriesv impedance branch comprises a compliance C, furnished by the diaphragm I9 or U, and a mass M. The interposed shunt impedance branch is constituted by a compliance C1 furnished by the plug 23. The mass M is equal to. the sum of two masses M1 and M2, where M1 is equal to half the mass of the plug 23 and M2 is the equivalent mass of the diaphragm I'9 or 2|. In accordance With wellestablishedv practice the electrical symbol for capacitance is used for the compliances C and C1 and the symbol for. inductance is. used for the mass M.

The values of C, C1. and. M2,, in mechanical units,

may be found from the following equations:

A (1-B-) TGW M =1 EK 63) in which A is theradius, D the area,. E the thickness. and K the density of the. d-iaphragin I9 or 2| Bis Poissons ratio and. F YounsFs modulusitherefor, and. G is the thickness. of, and H Youngs modnlusfor, the plug, 23.

The filter IZB. may be. designed to have, a trans-' mission. hand between a. lower cut-01f frequency f1 and an upper cut-ofi frequency in by giving the elements 0, C1 and. M thefollowing values:

m-m (6) where Z is the characteristic impedance of the filter at its mid-band irequency fm, defined as the. geometric mean of the cut-H3 frequencies f1. and f2. To avoid reflection effects the impedance Z should match the load impedances between. which. the filter operates.

The function of the filter units Hi is toconvert the shock wavegenerated within the container I0 into a vibration of longer duration but limited. frequency range, with its energy peaked at some chosen frequency; An analysis of the behavior of a shock wave impressed upon a bandpassfilter shows that the output vibration will be confined mainly to the hand between f1- and f2, will. have its energy peaked in the vicinity of the mid-band frequency fur and will persist for a time which is inversely proportional to the band width. Th mid-band frequency fin is, therefore, chosen to coincide with the desired frequency of the. energy peak and the band width is. made sufficiently narrow to ensure the required duration of the output vibration. The number of filter units I6 depends upon the power required to be radiated. The radiator shown in Figs. 1 and 2 has 21 of these units.

Fig. 4 is a sectional view of a cylindrical type of compressional wave radiator, and Fig. 5 is a sectional view taken along the line 5-5- of Fig. 4. Here th water-tight container 43 is formed of two concentric cylindrical shells 44, 45 and two end plates 46, 41. To facilitate assembly, the outer shell 44 is made in four quadrants such as 43 fastened together by means of bolts 49 through the adjacentfianges 5i! and 5|, as shown in Fig. 5. The end plate 46 is fastened to the outer cylinder 44 by means of screws such as 54 and the end plate 41 is fastened thereto by means of screws such as 55. The electrode 3| is mounted in. a central boss 58 in the end plate 46 and the opposite electrode 32 extends through an insulator 60 in a central hole in. the other end plate 4.1 to form a gap having its center 30 at the center of the container 43. The assembly is mounted onthe outside of a ship by means of the bolts 42 which go through the ships plate 6|. the end plate 41 and. an annular flange 62 on the. outer shell 44. A hole 63 in the ships plate BI permits electrical connections to be made to the end plate 4.1 and the insulated electrode 32 by means. of. the lead wires 39 and 4I, respectively, from a voltage source of the type shown. in Fig, 1. Thev gasket 61 keeps the water: out. of the ship- The inner shell. 45 has a. number of circular holes 64 drilled in. from the. outside and: it. is milled off fiat on the. inside as. shownat. 65. to form a number of inner diaphragms. 6.6. Corresponding. holes. 68 are drilled. in the outer shell. 44 from the inside and it is. milled ofi fiat on the outside. as. shown. at H1 to. form. the. outer diaphragms H. Between each pair of diaphragms 66 and H, and cemented thereto, is a cylindrical elastic plug 13 having its. outer corner beveledas shown. at 5 to facilitate. assembly of the four quadrants. 48.- of the outer shell 44.. Each pair of diaphragms 6 6 and II and the interposed plug 1.3 form a mechanical filter unit I8 which may be designed. in the same. manner as explained above. inconnection with: the unit I6 of Fig. 1 to? have the desired: mid-bandfrequency fin, cute-off frequenciesfiand f2- and. characteristic impedance Z. The radiator just described is. less directive in its radiating properties than is the one shown. in- Figs. 1 and 2 since it covers an arc of 360 degrees.

Figs. 6 and '7 showaradiator of. the: sphericaltype. Fig. 6 is: a side view, partly cut away and partly in section, showing the water-tight spherical container attached to the outside of. the

ships plate ill and Fig. 7' is a perspective View, partially exploded, showing certain of the parts. The container 89; comprises: a hollow spherical inner shell 82, made up of two hemispherical sections such as 84*, and a; spherical outer' shell 85, made in eight sections, such as 87; The inner shell 82 has a number of circul'arholes 88 drilled part way' through from the outside to form: the diaphragms 89 and the outer shell 86 has a cor:- responding' number of matching holes 9.0. drilled part way through from the inside to form the diaphragms 92'. Between each pair of diaphragms 89 and '92, and cemented thereto, is a cylindrical elasticv plug 93, similar to the plugs 23 and, 'I3-v described above. The plug 93 has its outer corner beveled as shown at 94 to facilitate assembly. The tiliaphragms 89 and. 9.2: and. the

interposed plug 93 forma mechanical filter unit similar to the units I6 and. I8, already described, and it may be designed in the same "way. All of the shell sections are bolted together by means of bolts such as 96 through adjacent flanges such as 91 and 98 to form a water-tighthollow sphere Within the container 89 are two electrodes (II and 32 separated by a gap the center 99 of which is at the center of thesphere. The electrode -3I is electrically connected to the inner shell82 but the electrode 32 is insulated from 'the container 89 by means of the tubular insulator I90 within the protecting tube IO I. The leads 39 and M from the voltage sourceare connected, respectively, to the tube IOI and the electrode 32.

The container 80 is suspended from the ships plate8l by means of four rods I93, each of which is secured at one end to an outer plate I04 and is held in place by means of the four bolts I95 which go through the outer plate I94, the ships plate 8| and the inner plate I96. The other end of the rod I93 goes through holes in the lugs I98 and I9 9 associated, respectively, with the upper half and the lower half of the outer shell 86 and, with the aid of the nuts III and III, holds the two halves of the shell 86 together. The tube IIlI enters the ship through a ho1e'II2 in the plate 8| made water-tight by means of the packing box H3 and packing material H4.

The spherical type of compressional wave radiator shown in Figs. 6 and '7 has some advantages over the other types of radiators disclosed herein. Since the shock wave is generated at the center 99 of the inner spherical shell 82 it sets up a spherical compressional wave which reaches all the filter units, and all portions of each inner diaphragm 89, at the same time and in the same phase. The output energ from all of the filter units will, therefore, be in phase and possible interference between units will be avoided. A further advantage is that the output energy from the radiator will also be very nearly a spherical Wave and will be radiated in all directions with substantially equal intensity.

What is claimed is:

1. A compressional wave radiator comprising a water-tight container, liquid within said container, means for delivering a strong impulse to said liquid and filtering means associated with said container for transmitting therethrough a band of frequencies while attenuating frequencies outside of said band, said filtering means including a plurality of mechanical filter units and each of said units comprising two diaphragms rigidly supported at their peripheries and an interposed layer of elastic material having a comparatively low Youngs modulus.

2. A compressional wave radiator in accordance with claim 1 in which a plurality of said filter units are located substantially equidistantly from the point of delivery of said impulse.

3. A compressional wave radiator comprising a water-tight container, liquid within said container, means for delivering a strong impulse to said liquid and filtering means associated with said container for transmitting therethrough a band of frequencies while attenuating frequencies outside of said band, a portion of said container being constituted by an inner wall and an outer wall, said inner wall having a number of holes extending part way through from the outside to leave comparatively thin inner diaphragms, said outer wall having the same number of matching holes extending part way through from thei-nside to leavecomparatively thin outer diaphragms and said filtering means including elastic plugs insertedrespectively between said inner diaphragms and the corresponding outer p mi s v q. i

4. A compressional 'wave radiator comprising a parabolic reflector, an inner plate and an outer plate closing said reflector-to make awater-tight container, liquid within-'said-container, means for delivering a strong impulse to 'said liquid near the focus of said parabolic reflector and I a plurality of mechanical filter units'associatedwith said plates for transmitting therethrough a band of frequencies while attenuating frequencies out side of said-band, each of said filter units comprising two diaphragms rigidly supported at their peripheries and aninterposed layer of elas'e tic material having a comparatively low Youngs modulus. a

1 5. A compressional wave radiator comprising a parabolic reflector, an inner plate andan outer plat'efclosing said reflector to make a water-tight container, liquid'within said container, means for delivering a strong impulse to said liquid near the focus ofsaid parabolic reflector and a'plurality of mechanical filter units associated with said plates for transmitting therethrough 'a band of frequencies while attenuating frequenciesfiout side of said band; said inner plate having a number of. holes extending part way through from ,the outside to leave comparatively thin inner diaphragms, said outer plate having the same number of matching holes extending part way wall, end. plates closing said cylindrical walls to make a water-tight container, liquid within said container, means for delivering a strong impulse to said liquid near the center of said container and a plurality 'of mechanical filter units associated with said cylindrical walls for transmitting therethrough a band of frequencies while attenuating frequencies outside of said band, each of said filter units comprising two diaphragms rigidly supported at their peripheries and an interposed layer of elastic material having a comparatively low Youngs modulus.

'8. A compressional wave radiator comprising an inner cylindrical wall, an outer cylindrical wall, end plates closing said cylindrical walls to make a water-tight container, liquid within said container, means for delivering a strong impulse to said liquid near the centerof said container and a plurality of mechanical filter units associated with said cylindrical walls for transmitting therethrough a band of frequencies while attenuating frequencies outside of said band, said inner cylindrical wall having a number of holes extending part way through from the outside to leave comparatively thin inner diaphragms, said" outer cylindrical wall having the same number of matching holes extending part way through from the inside to leave comparatively thin outer diaphragms and each of said filter units including an elastic plug inserted between one of said a 7 inner diaphragms and the corresponding outer dia hragm.

9. A compressional wave radiator in accordance with claim 7 in which a plurality of said filter units are located substantially equidistantly from the point of delivery of said impulse.

10. A compressional wave radiator comprising a hollow spherical inner shell and a spherical outer shell constituting a water-tight container, liquid within said container, means for delivering a strong impulse to said liquid near the center of said container and apluralityof mechanical filter units associated with said shells for transmitting therethrough a band of frequencies while attenuating frequencies outside of said band, each of said filter units comprising two diaphragms rigidly supported at their peripheries and an interposed layer :of elastic material having 'a comparatively low Youngs modulus.

.1 1. A compressional wave radiator comprising a hollow spherical inner shell and a spherical outer shell constituting a water-tight container, liquid within said container, means for delivering'a strong impulse to said liquid near the center of said container, and a plurality of mechanical filter uni-ts associated with said shells for transmitting therethrough a band of frequencies while attenuating frequencies outside of said band, said inner shell having a number of holes extending part way through from the outside :to leave-comparatively thin inner diaphragm, said outer shell having the same number of matching holes extending part way through from the inside to leave comparatively thin outer diaphragms and each of said filter units including-an elastic fplug inserted between one of said inner diaphragms and the corresponding outer diaphragm.

1 2. A compressional wave radiator in accordance with claim 10 in which a.plurality of :said filter units are located substantially 'e'quidistantly from the point of delivery 'of said impulse.

13. A wave filtering device comprising an inner plate, an outer .plate and a plurality of )plugs of elastic material having a comparatively low Youngs modulus, said inner plate :having a mim ber of holes extending part way through from the outside to leave comparatively thin inner diaphragms, said outer plate having the same num* ber of matching holes extending part way through from the inside to leave comparatively thin outer diaphragms and said ,plu'gs being in serted, respectively, between said inner "dia phragms and the corresponding outer diaphragms.

14. A wave filtering device in accordance with claim 13 in which said plugs are cemented to said diaphragms.

WARREN P. MASON. 

